Question 310281
Use a ratio
You know that a yardstick is 3 feet long. 
Also the yardstick shadow is given in inches, and the flagpole shadow is given in feet. We need to convert inches to feet.
The yardstick shadow is 15/12 feet
So
{{{3/(15/12) = PoleHeight/20}}}
{{{60/(15/12) = Poleheight}}}
{{{60*12/15 = PoleHeight}}}
{{{4*12 = PoleHeight}}}
{{{48 = PoleHeight}}}
The flagpole is 48 feet tall